This invention is directed to transparent articles prepared from thermoplastic compositions having high flow and ductility, and in particular to optical lenses prepared from thermoplastic compositions comprising a poly(aliphatic ester)-polycarbonate copolymer.
Miniaturization, functionality integration and weight reduction are emerging trends in portable hand-held electronics. These devices must withstand everyday usage over their lifetime, which can be up to several years. These trends call for plastic materials having enhanced flow properties with the ability to fill thinner wall designs, and excellent impact performance over a variety of usage environments (for example, physical shock due to dropping the item, and extremes of temperature and humidity).
The ability to take high quality pictures with devices such as mobile phone cameras or other portable handheld devices thus necessitates the need for materials, and in particular lens materials, with better properties. A camera embedded into any of these portable devices typically includes a complex optical system of a matched series of lenses, each of which has distinct optical characteristics, so that the resulting lens system as a whole has a variety of capabilities to meet consumer needs.
Polycarbonates, relative to other thermoplastics, are noted for their exceptional optical properties, thermal resistance, and mechanical properties such as impact strength. Currently, exemplary commercially available materials for the fabrication of such lenses or lens systems includes materials such as, for example, bisphenoxyethanol polyesters including OKP4 and OKP4-HT, available from Osaka Gas Chemicals Co, but which are prepared from expensive specialty feedstocks. However, high flow, optical quality polycarbonates remain the incumbent material of choice for lens materials due to their high optical and mechanical performance properties and low-cost, readily available feedstocks. However, as the lenses become smaller and smaller, and the quality requirements (e.g. picture size, quality) become more stringent, the performance of commercial optical quality polycarbonate is no longer adequate.
Transparent polymer compositions with low haze are desirable for versatile, low cost, high volume manufacture of optical grade components such as lenses for goggles and face shields, light guides and panels, and for more rigorous applications such as digital photography. While glass and various highly transparent thermoplastics may be used, the currently available materials require either long processing time (such as for the grinding of glass lenses), or for plastics, have undesirable thermal properties (as with polymethyl methacrylate) or high birefringence (such as with many optical grade commercial polycarbonates).